USING HEC-RAS AND QUAL2E TO ASSESS JOHOR RIVER WATER
QUALITY
ALI H. AHMED SULIMAN
UNIVERSITI TEKNOLOGI MALAYSIA
USING HEC-RAS AND QUAL2E TO ASSESS JOHOR RIVER WATER
QUALITY
ALI H. AHMED SULIMAN
A project report submitted in partial fulfilment of the requirements
for the award of the degree of Master of Engineering
(Civil-Hydraulics and Hydrology)
Faculty of Civil Engineering
Universiti Teknologi Malaysia
“To my beloved father Mr. Hussien Ahmed Sulieman and my mother Mrs. Ekbal Abdul
Fatah, to my brother as well as to all my sisters. I would say to them, I am very proud of
you, thanks for your encouragement, supportive situations. Conversely, to all my best
friends thank you for being faithful and helpful”
To my supervisor, ASSOC. Prof. Ir. Dr. AYOB KATIMON, your good deeds will always
be remembered.
Lastly, to all my fellow friends,
Thanks for everything…
ACKNOWLEDGEMENT
First of all, my praises and thanks to Almighty Allah, the Most Gracious the
Most Merciful, who gave me the knowledge, encouragement and patience to
accomplish this research May the peace and blessings of Allah be upon our Prophet
Mohammad.
I wish to express my sincere appreciation and thanks to my supervisor, Prof. Dr.
AYOB KATIMON, for encouragement when I have problems, guidance to the right
way, and suggestions when I am hesitate. Without his continued support and interest,
this project report would not have been the same as presented here.
I am also indebted to Universiti Teknologi Malaysia (UTM). I also need take
this opportunity to say very thankful to my FKA staff for their guidance, advice and
knowledge in this field for help me successful finished my project. Without their
contribution, interest and guidance I would not complete this study.
Last but not least, to all my family members and friends who have directly or
indirectly helps and contribute to the success of this project.
ABSTRACT
Johor River is a major raw water supplier for a highly populated region,
Johor state as well as Singapore. Because of the development over the entire
catchment, water quality has become a sensitive matter. For this reason, several
studies have been carried out in order to investigate its affects on the
environment. Computer simulation and Numerical model are considered as
essential and powerful tools in water resources monitoring plan in decisionmaking process. HEC-RAS is integrated system software designed to perform
one dimensional hydraulic calculation. It was used to estimate the hydraulic
changes due to the hydrological alteration of Johor River in response to the
change of river discharges and to calculate the sediment transport capacity. Also
in this study, QUAL2E was used as the water quality modeling analysis tool. It
is suitable for one-dimensional analysis with constant flow and it is applied to
predict the water quality model for the Johor River. The model was used to
simulate both dissolved oxygen (DO) and biological oxygen demand (BOD )
along the certain reach of the river. Data was collected from several stations
along Johor River, ranging from Rantau Panjang till water treatment plant. Flow
rates, depths, loads, dissolved oxygen, and length of the river were measured in
the field. Moreover, biochemical oxygen demands concentrations and total
suspended solid were measured in the libratory. Those entire databases were
used to supply inputs to the two models. As first time the HEC-RAS has been
used to model; and followed by QUAL2E for simulating water quality at Johor
River. Also In order to assess the vegetation buffer strips’ performance, and
because of the reducing of the light penetration, harmful algal blooms, decrease
in dissolved oxygen, total suspended solid (TSS) was estimated. All parameters
are compared to the Interim National Water Quality Standard (INWQS)
provided by Department of Environment (DOE). From the finding, the average
concentration of suspended solid was 17.97 mg/l. The trap efficiency for
pollution load reduction by vegetation buffer strip was estimated 9.17 % and this
value would be bigger during high discharges.
ABSTRAK
Sungai Johor merupakan pembekal air mentah utama untuk daerah yang
sangat padat di negeri Johor serta Singapura. Kerana pembangunan pesat,
ketinggian air telah menjadi masalah sensitif. Untuk alasan ini, kajian telah
dilakukan untuk menyiasat kesan ruya terhadap persekitaran. Simulasi komputer
dan model berangka dianggap sebagai alat penting dan berkuasa dalam
pemantauan sumber daya air di dalam proses membuat keputusan. HEC-RAS
terintegrasi perisian sistem yang direka untuk melakukan perhitungan hidrolik
satu dimensi. Ini digunakan untuk menganggarkan perubahan hidrolik kerana
perubahan hidrologi Sungai Johor dalam menanggapi perubahan rejim sungai
dan untuk mengira kapasiti pengangkutan sedimen. Juga dalam kajian ini,
QUAL2E digunakan sebagai alat analisis pemodelan ketinggian air. Sangat
cocok untuk analisis satu-dimensi dengan arus konstan dan itu tersirat untuk
memprediksi model ketinggian air bagi Sungai Johor. Model ini digunakan
untuk simulasi kedua oksigen terlarut (DO) dan keperluan oksigen biologi
(BOD5) sepanjang liputan tertentu sungai. Data dikumpul daripada beberapa
stesen di sepanjang Sungai Johor, pemprosesan air bermula dari Rantau panjang.
Nelai Arus, kedalaman, beban, oksigen terlarut, dan panjang sungai diukur di
lapangan. Selain itu, permintaan oksigen biokimia dan konsentrasi total pepejal
tersuspensi diukur dalam makmal. kesemua database digunakan sebagai input
kepada dua model. Pertama, HEC-RAS telah digunakan untuk model, dan
diikuti oleh QUAL2E untuk simulasi high air di Sungai Johor. Juga Untuk
menilai prestasi jalur penyangga vegetasi, pengurangan penetrasi cahaya, mekar
alga berbahaya, penurunan oksigen terlarut, total suspended solid (TSS)
dianggarkan. Semua parameter yang dibandingkan dengan Kualiti Air
Kebangsaan Interim Standard (INWQS) disediakan oleh Jabatan Alam Sekitar
(DOE). Dari laporan tersebut, maka konsentrasi paurate bahan teranpai adalah
17,97 mg / l. Kecekapan perangkap untuk pengurangan beban pencemaran oleh
vegetasi buffer dianggarkan 9.17% dan nilai ini akan lebih besar mengilcut
kadar aliram sungai.
TABLE OF CONTENTS
CHAPTER
TITLE
PAGE
TITLE
i
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xi
LIST OF FIGURES
xiii
1
2
INTRODUCTION
1.1
Introduction
1
1.2
Statement of the Problem
4
1.3
Objective
5
1.4
Scope of study
5
LITERATURE REVIEW AND MATHEMATICAL
MODELING
2.1
General
6
2.2
Water pollution
7
2.2.1
Point Source
7
2.2.2
Non-Point Source
8
2.3
Water Quality Monitor
9
2.4
Water Quality Parameters
11
2.4.1
Dissolved Oxygen (DO)
12
2.4.2
Biochemical Oxygen Demand (BOD)
13
2.5
2.4.3 pH
14
2.4.4
15
Total suspended solid (TSS)
HEC-RAS Overview
15
2.5.1
Steady Flow Water Surface Profile
16
2.5.2
Energy Head Loss
18
2.5.2.1
Friction Loss Evaluation
19
2.5.2.2
Contraction and Expansion
19
Loss Evaluation
2.5.3
3
Assumption in Steady Flow Program
20
2.6
Riparian Buffer Strip
20
2.7
Sediment Transport Capacity in HEC-RAS
25
2.7.1
Fall Velocity
28
2.7.2
Sediment Transport Function
30
2.7.1.2
30
Toffaleti Method
2.8
Water Quality Modeling
33
2.9
Limitation of QUAL2E
36
2.10
QUAL2E Calibration and Validation
37
2.11
Applications of QUAL2E
38
METHODOLOGY
3.1
Introduction
40
3.2
Location of Study Area
42
3.3
Data Collection
43
3.3.1 Water Sampling and its Stations
44
3.3.2 Flow Measurement
48
3.4 In-Situ Testing
51
3.5
52
Water Quality Test
3.5.1 Total Suspended Solid
3.5.2 Biochemical Oxygen Demand (BOD)
3.6
52
55
Interim National Water Quality Standards
(INWQS)
55
3.7
Sieve Analysis
58
3.8
Calibration of Qual2E Model
59
3.9
Validation of QUAL2E Model
60
4
EXECUTION STEPS AND RESULTS
4.1
Johor River Modeling
62
4.2
HEC-RAS Interface
63
4.3
Starting a New Project
63
4.4
Entering Geometry Data
64
4.4.1 River System Schematic
64
4.4.2 Cross Section Geometry
65
Steady Flow
66
4.5.1
Boundary Condition
66
4.5.2
Discharge Information
67
4.5
4.6
Steady Flow Analysis
68
4.7
Sieve Analysis
74
4.8
Sediment Transport Capacity
76
4.9
Analysis the Data for QUAL2E
81
4.10
Comparison between Calibrated
81
and Observed Data
5
4.11
Total Suspended Solid of Johor River
83
4.12
pH Analysis
85
CONCLUSION AND RECOMMENDATION
5.1
Conclusion
86
5.2
Recommendations
88
REFERENCES 90
LIST OF TABLES
TABLE NO
2.1
TITLE
PAGE
Some Recommended Widths of Vegetate Buffer
Strips, for Various Functions
24 2.2
limitation of data in QUAL2E
37
3.1
The Calculation of Discharge Using
51
Velocity-Area Method
3.2
Interim National Water Quality Standards
56
(INWQS)
3.3
Data Needed to Run QUAL2E Program
60
4.1
Sediment Transport Potential
78
4.2
Data for Johor River from Sampling
4.3
Total Suspended Solid Concentration from
81
84
Laboratory Testing in unit mg/l or ppm.
4.4
The pH values from IN-SITU Testing
85
LIST OF FIGURES
FIGURE NO
TITLE
PAGE
2.1
The relationship between BOD and DO of a River System
13
2.2
Representation of Terms in the Energy Equation
17
2.3
Riparian Buffer with Three Zones
21
2.4
The relationship between particle sieve diameter
31
and its fall velocity
2.5
QUAL2E computational network
36
3.1
The overall processes involved in this study
41
3.2
Johor River Basin
42
3.3
Buffer Strips at Johor River
43
3.4
The Exact Location of the River Sampling Stations
44
3.5
The surface water level at Rantau Panjang Station
45
3.6
The Submergence area Vegetation Buffer Strip
45
3.7
The place of Water Samples within the Cross-Section of the
46
River
3.8
Water Sampling Using Van Dorn Sampler in order to Pick the
47
Samples from the River
3.9
Polystyrene Box and the Bottles used to Collect Water
47
Samples
3.10
Schematic Picture Demonstrating Flow Rate Using Velocity-
48
Area Method
3.11
Current Meter
49
3.12
DO Meter
52
3.13
Apparatus for Total Suspended Solid Test
54
3.14
The sieves and the shaker machine
58
3.15
The Instrument used to Weighed the Sample Retained
59
4.1
The HEC-RAS Main Window
64
4.2
New Project Window
64
4.3
River System Schematic of Johor River
65
4.4
Cross Section Window
66
4.5
Steady Flow Boundary Condition Editor
67
4.6
Steady Flow Data Editor
68
4.7
Steady Flow Analysis Window
68
4.8
Cross Section Plot at Station one at Rantau Panjang
69
4.9
Cross Section Plot at Station Two
70
4.10
Cross Section Plot at Station Three
70
4.11
Cross Section Plot at Station Four
71
4.12
Cross Section Plot at Station Five at the Bridge
71
4.13
Profile Plot
73
4.14
General Profile Plot
72
4.15
Rating Curve
73
4.16
X-Y-Z Perspective Plots
73
4.17
Details Tabular of Cross Section
74
4.18
The Result of Sieve Analysis
75
4.19
Sediment Transport Capacity Window
76
4.20
Sediment Rating Curve Plot for all Stations for Profile one
79
4.21
The Sediment Profile Plot
80
4.22
Comparison between Calibrated and Observed Data for
4.23
Oxygen Demand Concentration
82
Comparison Between Calibrated and Observed Data for
83
Biochemical Oxygen Demand Concentration
1
CHAPTER 1
INTRODUCTION
1.1
Introduction
Water plays an important role in our daily life and without it no life on the
earth. Most activities in our life depend on water such as agriculture, drinking, a
medium of transportation and many more. In fact, many great civilizations have
started at near to the source of water whether river or stream, such as Mesopotamia,
Egypt, and many more.
According to the study of Hydrology, river is defined as a natural stream flow
in a channel. River water quality is affected by a wide range of natural and human
pollution. The most important of the natural pollution are geological, hydrological
and climatic. Water pollution occurs when a body of water is unfavorably affected
by the addition amount of bad materials to the water body. It can come from a
number of different sources. If the pollution comes from a single source, like oil leak,
2
we called it, point-source pollution. While, the pollution that comes from many
unknown sources called, non-point source pollution. Approximately, all the pollution
types affect the immediate area surround for that source. Sometimes the pollution
may affect the environment for miles away from the source. The effects of water
pollution are not just hurtful for people, but it has effects on habitat such as animals,
fish, and birds. It can destroy the aquatic life and reduces its productive ability. It is
also hazardous to human health, and overall water supply system.
In Malaysia, there are 1800 rivers comprising 150 systems that run up to
38000 km. As in many part of the world, water from rivers in Malaysia is used
extensively for domestic needs, agriculture, drinking, cooking, washing, and many
other purposes. One of those rivers is Johor River. It is very important fresh water
supply to the treatment plant located at Kota Tinggi which distributed treated water
to eater local need. The water quality of Johor River has been deteriorated with
increasing level of various pollutants. This contaminant eventually flow into Johor
River from the area neighbor it.
Computer simulation and numerical model is one of the best ways for
hydrodynamic study and controlling the water quality. It is powerful and essential
tool to monitoring plan in making decision related to the parameters of the water
quality. We can compile and analyze the hydrodynamic data and the water quality
parameters data for a particular length of river to evaluate river water quality.
HEC-RAS is an integrated system composed of separate hydraulic analysis
components, data storage and management capabilities, graphics, and reporting
facilities. The system ultimately contains three one-dimensional hydraulic analysis
3
components for (1) steady flow water surface profile computations, (2) unsteady
flow simulation, and (3) moveable boundary sediment transport computations. All
three components use a common geometric data representation and common
geometric and hydraulic computation routines. In addition, the system contains
several hydraulic design features that can compute the basic water surface profiles.
Qual2e is a one-dimensional mathematical model. It is available as free
software to simulate river water quality. It is a multi-purpose model for determining
the quality of stream flow by allowing the simulation of fifteen parameters associated
to water quality in any reach of river chosen by researcher. The model is applicable
to well mixed streams and considers the transport mechanisms – dispersion and
advection – significant only along the main direction of flow (longitudinal direction).
When the discharge decrease as well as the depth of water will reduce, the
vegetation buffer strip area will increase within the river. So, this area can play as
filter to intercept the sediment transport capacity. Riparian buffer is the area of
permanent vegetation (trees, shrubs and grass) neighbor surface water bodies, and are
to improve water quality by trapping or removing various non-point source pollutants
from over land and shallow subsurface flowing in the same time [14]. It is important
to use vegetation buffers in reducing the contaminant to the river especially before or
during the high discharges.
4
1.2
Statement of the Problem
The development over the entire world leads to more concentration on water
quality which is consider as a sensitive matter and has affects on humans and
environment. The contamination loadings in Johor River come from many sources as
a non-point source contamination, when the rain falls on catchment area surround
Johor River. The contaminant substances are carried by runoff, and before the
contaminants enter the water body, they pass through the buffer zones to pour in
watershed or directly to the river. This would create many problems for the water
quality status such as decrease in dissolved oxygen, harmful algal blooms, and
reduced light penetration. Moreover, the sediment transport capacity also consider as
a serious problem which is affect on the flow depth and bed river condition. The
study on hydrological characteristics of river is so important for future development
especially in water resources engineering in term of water resource management.
The aim of this study is to determine and analyze the concentration of some
parameters which are considered as important parameters to cover river water
quality. These parameters are Dissolved Oxygen (DO), Biochemical Oxygen
Demand (BOD), Total Suspended Solid (TSS), and PH, and also sediment transport
capacity for several cross sections. Because the raw water of the Johor River is used
to supply the domestic requirement, therefore, all these parameters are compared to
the Interim National Water Quality Standard (INWQS) provided by Department of
Environment (DOE).
5
1.3
Objective of Study
1. To estimate a hydrological model for 5000 m of Johor River using HECRAS.
2. To predict the fluctuation water level for and sediment transport capacity for
different discharge using HEC-RAS.
3. To analyze and simulate water quality for Johor River using QUAL2E
program.
4. To estimate the typical concentration of suspended solid and trap efficiency
of the vegetation buffer strip along the Johor River.
1.4
Scope of Study
The scope of this study is as follows:
1. Buffer zones identification.
2. Water quality sampling and the analysis in the lab after we bring the samples
from the site.
3. IN-SITU testing.
4. Sediment transport capacity calculation.
5. Getting Samples from the river for grain size test.
6
CHAPTER 2
LITERATURE REVIEW
2.1
General
Water quality is an important issue in public policy for decades, and
many attempts have been expended in developing effective water management
strategies to ensure sufficient high-quality water supplies [21].
Water constitutes around 70% of the Earth's surface land and it is an
important resource whether for people who live on the plant or for the
environment. Water can be formed as rivers, lakes and oceans as well, and the
effects of contaminant leading to the degradation of the entire ecosystem.
This study is utilizing a software HEC-RAS and QUAL2E, and
explore some information on water pollution as well as buffer strips provision.
7
2.2
Water Pollution
Water is one of the most important things which the human has used
more than any other resource in his life. Most of the water on the earth is stored
in oceans and ice caps which is so dear for our diverse needs. Most of our
demand for water comes from rain water deposited in surface and ground water
resources. Pollution of water is one of the most significant environmental
problems of the recent decades. Pollution of water has its origin mainly in
urbanization, industrialization, agriculture and increase in human population.
Water can be regarded polluted when it gets changed in its quality or
composition either naturally or as a result of human activities so as to become
less suitable for drinking, domestic, agricultural, industrial, recreational, wildlife
and other uses for which it would have been otherwise suitable in its natural or
unmodified state [13]. Water pollution can come from a number of different
sources. If the pollution comes from an identifiable source such as an oil spill, it
is called point-source pollution. If the pollution comes from many sources, it is
called nonpoint-source pollution. The causes of water pollution include sewage
and waste water, industrial waste and oil pollution. Storm water runoff typically
contains significant amounts of anthropogenic pollutants as well as naturally
occurring materials.
2.2.1
Point Sources
Point source pollution comes from a specific place that can be
considered as the source of the pollution which has unfavorable influence on
river water. For example, an industrial site with a pipe directly dumping without
treated pollutants into a water source. Point source pollutants are most often
8
minerals, chemicals, and sewage and it affect river, lakes as well as coastal area.
Also, point source is easy to monitor and control compared to non-point source.
2.2.2
Non-Point Sources
Non-point source pollution is the pollution of water resources from a
wide variety of human activities that take place over a large geographic area.
Non-point pollution comes from farms, cities, forests, mining operations,
construction sites, and also homes. It occurs when runoff from rain carry
pollutants to the rivers. These pollutants include sediments (soil), fertilizers, and
nutrients, oils and grease, pesticides, toxic chemicals, road salts, domestic animal
waste untreated sewage from homes not hook-up to a city or community
wastewater treatment plant, and other contaminants.
The most common non-point sources pollutants are sediments,
nutrients, and sewage. Because non-point sources pollution is diffuse, it is very
difficult to pin point its origin, in comparison with the point source, the reducing
or removing non-point sources pollution is more difficult. Also, large quantities
of Pollutants which come from non-point sources pollution enter water sources
during rainfall or thunderstorm.
Ways to reduce non-point sources pollutants, manage storm water
runoff, and minimize the amount of pollutants which enter rivers should be
found. Because non point source pollution has problem that may affect our life, it
is necessary to convince individuals, and society as a whole, that there is a
problem and a compelling need for action which will lead to make Changing's in
lifestyles and behaviors needed to prevent this type of pollution.
9
In this study, we will consider a length of river and its surrounding an
agricultural area. So, the responsibility of farmers to grow their crops and graze
their animals in ways which protect nearby streams will be important as well as
to apply lawn care chemicals and fertilizers carefully and safely or use
environmentally friendly products. Furthermore, this responsibility applies also
to the people who harvest timber to do so in ways that prevent soil runoff. We
know this task will not be easy, and it will not be inexpensive, but the price of
avoiding the issue grows daily.
2.3
Water Quality Monitoring
Water is the important item in our life because human being cannot
survive without water. It is cover around 78% of entire earth surface representing
and 22% of our earth consists of land. From the 78%, 97.2 % from the portion
consists of sea water, and 2.15% consists of ice water. While 0.65% consists of
surface water.
Water sources commonly used are surface waters; rivers and lakes,
groundwater and sea water. Water is used for various purposes in our life; it is
used for a community, domestic uses, commercial, industrial, public use, and for
fire quenching demands. The Author stated that water is provided by nature so
generously that most of us take it for granted and use it without ever considering
how little we know about it. The three factors of life in order of importance are
air, water, and food. Water is considered one of the four elements by the ancients
people with the others being earth, fire, and air. Without adequate usable water,
the whole structure of our society would collapse.
10
The usage and importance of water cannot be denied anymore, for
that reason, water quality should be monitoring as far as it should be. [35] Stated
that, “Water quality” is a term used to express the suitability of water to sustain
various uses or processes.
Any particular use will have certain requirements for the physical,
chemical or biological characteristics of water; for example limits on the
concentrations of toxic substances for drinking water use, or restrictions on
temperature and pH ranges for water supporting invertebrate communities.
Consequently, water quality can be defined by a range of variables which limit
water use.
Although many uses have some common requirements for certain
variables, each use will have its own demands and influences on water quality.
[35] Said that freshwater is a finite resource, essential for agriculture, industry
and even human existence.
Water pollution and wasteful use of freshwater threaten development
projects and make water treatment essential in order to produce safe drinking
water. Discharge of toxic chemicals, over-pumping of aquifers, long-range
atmospheric transport of pollutants and contamination of water bodies with
substances that promote algal growth (possibly leading to eutrophication) are
some of today’s major causes of water quality degradation.
Accelerated eutrophication results from enrichment with nutrients
from various origins, particularly domestic sewage, agricultural run-off and agroindustrial effluents. Lakes and impounded rivers are especially affected.
Agricultural land use without environmental safeguards to prevent overapplication of agrochemicals is causing widespread deterioration of the soil or
11
water ecosystem as well as the underlying aquifers. The main problems
associated with agriculture are salanisation, nitrate and pesticide contamination,
and erosion leading to elevated concentrations of suspended solids in rivers and
streams and the siltration of impoundments. Irrigation has enlarged the land area
available for crop production but the resulting salanisation which has occurred in
some areas has caused the deterioration of previously fertile soils.
Direct contamination of surface waters with metals in discharges from
mining, smelting and industrial manufacturing is a long standing phenomenon.
However, the emission of airborne metallic pollutants has now reached such
proportions that long-range atmospheric transport causes contamination, not only
in the vicinity of industrialized regions, but also in more remote areas. Similarly,
moisture in the atmosphere combines with some of the gases produced when
fossil fuels are burned and, falling as acid rain, causes acidification of surface
waters, especially lakes. Contamination of water by synthetic organic micropollutants results either from direct discharge into surface waters or after
transport through the atmosphere. Today, there is trace contamination not only of
surface waters but also of groundwater bodies, which are susceptible to leaching
from waste sumps, mine tailings and industrial production sites.
2.4
Water Quality Parameters
Physical, chemical and biological are the categories which are used to
figure out water quality. Therefore, for this study we will concentrate on
Dissolved Oxygen (DO) and Total Suspended Solid (TSS), for physical
parameter. Moreover, Biochemical Oxygen Demand as a chemical parameter. In
addition, pH which is used to evaluate the concentration of hydrogen ion will be
looked too.
12
2.4.1
Dissolved Oxygen (DO)
Dissolved Oxygen is representing the amount of molecular oxygen
dissolved in water. It represents the amount of molecular oxygen dissolved in
water. It is the most common parameter in observing the water quality.
According to [8], the minimum DO is 2 mg/l need to maintain higher life form
and 4-5 mg/l to survive natural stream.
There are many factors that can affect DO level like the industries
effluent such as food processing and paper production. Also, there are a natural
influence like animal’s droppings and crop residues. The microorganism’s is
leading to convert the biodegradable organics substance into stable end products.
So, during this process DO will be consumed where the rate and quantity
depends on the amount of organic discharged and the dilution of the water
stream. on other hand, the mechanism of reaeration from atmosphere and the
process of photosynthesis by aquatic plant supply the DO in the river.
Oxygen deficit is the different between the actual DO concentration
and the DO saturation. The oxygen deficit and the temperature control the rate of
oxygen transfer from air to the water surface; the large value of oxygen deficit is
creating the faster rate of oxygen transfer taking place. The presence of sunlight
and nutrient in the water help algae produce oxygen. Also, the excessive growths
of algae or algal bloom from a layer that cover stream surface reduce the
intensity of light penetration and cause the stress on algae. Thus it will die off
and turn into oxygen-demanding organic matter as bacteria necessitate degrading
them.
13
2.4.2
Biochemical Oxygen Demand (BOD)
Biochemical oxygen demand (BOD) is a measure of the amount of
oxygen that bacteria will feed while decomposing organic matter under aerobic
conditions. It is an empirical one which determines the relative oxygen
requirements of the various organic substances present in water as they are
biodegraded by aquatic microorganisms. Microorganism need some amount of
oxygen to oxidize organic wastes in aerobic condition. The amount of the oxygen
is called biochemical oxygen demand (BOD), usually expressed in milligram per
liter of wastewater (mg/l) [28]. BOD is the most important parameter to control
in pollution. It is used as measurement of organic pollution as basics to estimate
the required oxygen for biological processes, and as an indicator of process
performance. Thus the higher value of BOD means the higher of oxygen deplete
in a river. The standard for BOD test is to be run under 20 C for five days and
defined as five day BOD or the use of oxygen in first five days of biodegradation
by microorganism. Based on the value of BOD, water can be divided into four
zones, namely clean, decomposition zone, septic zone, and recovery zone. The
value of BOD is against the value of DO in the water. Therefore, when the value
of BOD is high in water, value of DO will be low and when the value of BOD is
low, the value of DO will be high, as shown in Figure (2.1) below.
Figure 2.1: The relationship between BOD and DO of a River system [7]
14
2.4.3
pH
pH is known as measure of the hydrogen ion concentration; pH of 7.0
indicates a neutral solution, pH values smaller than 7.0 indicate acidity, pH
values larger than 7.0 indicate alkalinity. Water generally becomes more
corrosive with decreasing pH; however, excessively alkaline water also may be
corrosive [40]. The pH of natural water depends on many factors such as
carbonate system; pH of clean water depends mainly on the concentration of
carbonates and carbon dioxide; carbonate waters are alkaline, whilst waters with
low concentrations of carbonates are usually acidic. It also depends on rock, from
which acidic or alkaline compounds can be weathered, types of soil in the
drainage area and also nature of discharged pollutants (wastewaters, atmospheric
deposits).
Surface water usually has pH values between 6.5 and 8.5, and only
rarely is outside the range of 4 to 9. The drainage water from forests and marshes
are usually acidic because of the presence of humid and fulvic acids. River
waters are usually more alkaline because of the presence of carbonates and
hydrogen carbonates.
The level of pH of water has an important influence on living
organisms and on many uses of the water. In waters which are too acidic or too
alkaline, there is very limited aquatic life, such as in some lakes that are receiving
acid deposition. The waters of these lakes are clear and clean but with few traces
of living organisms. The acid waters are especially detrimental to the water
supply system; for example, low pH accelerates the corrosion of metals. The
excessive acidification of surface waters accelerates the leaching out of heavy
metals and radionuclide’s from the bottom sediments. The pH of water also has a
great influence on the biochemical processes occurring in surface waters.
Alabaster and [47] have reviewed many aspects of pH in water.
15
2.4.4
Total Suspended Solid (TSS)
Suspended solid is the particles which are carried by discharge or the
dry weight after filtering a water sample, expressed in milligrams per liter. It
becomes sediment whenever these suspended particles settle to the bottom of the
river. Suspended solids consist of an inorganic fraction like (silts, clays, etc.) and
an organic fraction (algae, zooplankton, bacteria, and detritus) that are carried by
water as it runs off the land. The inorganic portion is usually considerably higher
than the organic. If the waters have high sediment loads, that lead to make it
obvious because of their "muddy" appearance. This is especially evident in
rivers, where the force of moving water keeps the sediment particles suspended.
The vegetation and its characteristics of a watershed affect the amount
of suspended solids. If the watershed has lots of firmly rooted vegetation, it will
act as a sponge to trap water and soil and thereby eliminate most erosion. If the
watershed has steep slopes and is rocky with little plant life, top soil will be
washed into the waterway during every rain.
2.5
HEC-RAS Overview
Hydrologic Engineering Center River Analysis System (HEC-RAS) is
software which is developed by the hydrologic Engineering Center of U.S army
Corp. it is being developed as a part of the “Next Generation” (NexGen) project.
The NexGen project encompasses several aspect of hydrology engineering,
including: rainfall-runoff analysis; river hydraulics; reservoir system simulation;
flood damage analysis; and real-time river forecasting for reservoir operation.
16
HEC-RAS is an integrated system of software, designed for interactive use in a
multi-tasking, multi-user network environment. It is designed to perform one
dimensional hydraulic calculation for a full network of natural or man-made
channels. This system uses a common geometric data representation and common
geometric and hydraulic computation routine to analyze:
1.
Steady flow water surface profile computations
2.
Unsteady flow simulation
3.
Movable boundary sediment transport computations.
4.
Water quality analysis
Steady flow water surface profile is a modeling system for calculating
water surface profile for steady gradually varied flow. It is capable of modeling
subcritical, supercritical and mixed flow regime water surface profiles.
The basis of computational procedure is based on the solution of the
one dimensional energy equation. Energy losses are evaluated by friction
(Manning’s equation), and expansion or contraction (coefficient multiplied by the
change in velocity head). The momentum equation is utilized in situations where
the water surface profile is rapidly varied. Moreover, the steady flow component
of HEC-RAS has a few special features. The special features are multiple plan
analysis, and split flow optimization at stream junction and lateral Weirs and
spillways.
2.5.1
Steady Flow Water Surface Profile
The computational procedure is based on the solution of one
dimensional energy equation. Water surface profiles from one cross section to the
17
next are computed by solving the energy equation with the standard step method.
The energy equation is written as:
𝑌𝑌2 + 𝑍𝑍2 +
𝛼𝛼2 𝑉𝑉22
𝛼𝛼1 𝑉𝑉12
= 𝑌𝑌1 + 𝑍𝑍1 +
+ ℎ𝑒𝑒
2𝑔𝑔
2𝑔𝑔
Where:
𝑌𝑌1 𝑌𝑌2 : Depth of water at cross-sections
𝑍𝑍1 𝑍𝑍2 : Elevation of the main channel inverts
𝛼𝛼1 𝛼𝛼2 : Velocity weighing coefficients
𝑉𝑉1 𝑉𝑉2 : Average velocities and equal to (Total discharge/Total flow area)
𝑔𝑔
ℎ𝑒𝑒
: Gravitational acceleration
: Energy head loss
Also, the diagram below is showing the term of the energy equation.
Figure 2.2: Representation of Terms in the Energy Equation
18
2.5.2
Energy Head Loss
The energy head loss, ℎ𝑒𝑒 is comprised of friction losses and
contraction or expansion losses. The equation for the energy head loss is as
follows:
ℎ𝑒𝑒 = 𝐿𝐿𝑆𝑆𝑓𝑓̅ + 𝐶𝐶 �
𝛼𝛼2 𝑉𝑉22 𝛼𝛼1 𝑉𝑉12
−
�
2𝑔𝑔
2𝑔𝑔
Where:
𝐶𝐶 : Expansion or Contraction loss coefficient
𝐿𝐿 : Discharge weighted reach length
𝑆𝑆𝑓𝑓̅ : Representative friction slope between two section
The distance weight reach length, L, is calculated as:
𝐿𝐿 =
𝐿𝐿𝑙𝑙𝑙𝑙𝑙𝑙 𝑄𝑄�𝑙𝑙𝑙𝑙𝑙𝑙 + 𝐿𝐿𝑐𝑐ℎ 𝑄𝑄�𝑐𝑐ℎ + 𝐿𝐿𝑟𝑟𝑟𝑟𝑟𝑟 𝑄𝑄�𝑟𝑟𝑟𝑟𝑟𝑟
𝑄𝑄�𝑙𝑙𝑙𝑙𝑙𝑙 + 𝑄𝑄�𝑟𝑟𝑟𝑟𝑟𝑟 + 𝑄𝑄�𝑙𝑙𝑙𝑙𝑙𝑙
Where:
𝐿𝐿𝑙𝑙𝑙𝑙𝑙𝑙 , 𝐿𝐿𝑐𝑐ℎ , 𝐿𝐿𝑟𝑟𝑟𝑟𝑟𝑟 : Cross section reaches length specified for flow in the left
overbank, main channel, and right overbank, respectively
𝑄𝑄�𝑙𝑙𝑙𝑙𝑙𝑙 , 𝑄𝑄�𝑟𝑟𝑟𝑟𝑟𝑟 , 𝑄𝑄�𝑙𝑙𝑙𝑙𝑙𝑙 : Arithmetic average of flows between sections for the left
overbank, main channel and right over bank, respectively
19
2.5.2.1
Friction Loss Evaluation
Friction loss is evaluated as product of friction of 𝑆𝑆̅ and L. Manning’s
equation is adapted to compute the friction slope at each cross section, the
equation is shown as:
𝑄𝑄 2
𝑆𝑆𝑓𝑓 = � �
𝐾𝐾
Where:
𝑆𝑆𝑓𝑓 : Representative friction slope between two sections
𝐾𝐾 : Conveyance for subdivision
2.5.2.2
Contraction and Expansion Loss Evaluation
Contraction occurred whenever the velocity head at downstream is
greater than the velocity head of upstream. Moreover, a flow expansion occurred
when the velocity head at upstream is greater than the velocity head of
downstream Equation used as stated below:
ℎ𝑐𝑐𝑐𝑐 = 𝐶𝐶 �
𝛼𝛼2 𝑉𝑉22 𝛼𝛼1 𝑉𝑉12
−
�
2𝑔𝑔
2𝑔𝑔
Where:
𝐶𝐶 : The contraction or expansion coefficient
20
2.5.3
Assumption in Steady Flow Program
a) Flow is one dimensional because the total energy head comprised in
equation is assumed to be the same for all points in a cross section
b) Slope of channel are assumed to be small because Y in equation (2.1)
is represented by the water depth measured vertically
c) Flow is assumed to be steady because the equation adapted does not
has any time-dependent terms
d) Flow is gradually varied flow type because the basis of information of
the equation is that the hydrostatic pressure distribution exists at each
cross section
e) Currently the program is not capable of dealing with movable
boundaries
2.6
Riparian Buffer Strip
Riparian Buffer Strip or vegetation buffer strip is a permanent vegetation
band neighbor to an aquatic system. It is used to maintain or improve water
quality by removing and trapping a non-point source pollutant. There are
different types of pollution such as contaminants from herbicides and pesticides,
nutrients from fertilizers, and sediment from upland soils. Indeed all come from
subsurface flow and overland flow.
Provision of providing sufficient width, [25] are emphasized that
buffer strip can improve water quality by intercepting non-point source pollutants
surface water flow. In another word, buffer strips is considered as a vital
requirement for water treatment plants than other expensive restoration
techniques.
21
Moreover, the buffer strip means transitional area between both
ecosystem for the water and the land. It is known as a source of nutrient for water
ecosystem. Furthermore, it serves as the fence of a stream or river which has a
certain width of trees, shrubs or grasses. It plays as a filter to intercept the
contaminants flowing from both sides of the river.
Buffer strips are formed in many shape like grassy buffers, grassed
waterways, or forested riparian buffer strips. Buffer strip may also provide a
numerous of functions. According to [44], a riparian buffer strips consists of
three zones:
•
Zone 1 is permanent woody vegetation immediately adjacent to stream
bank
•
Zone 2 is managed forest occupying a strip upslope from zone 1
•
Zone 3 is an herbaceous filter strip upslope from zone 2
Figure 2.3: Riparian Buffer with Three Zones
The purpose of zone 3 of the buffer strip is to remove sediment from
surface runoff. Also, the primary function of zone 2 is to intercept movement of
22
sediment and other chemical pollutants which come from upland areas into
wetland area. The vegetation proposes is to reduce the velocity of the runoff and
play as a barrier to sediments moving as well as it is produces organic matter
which creates chemical and biological processes which transform pollutants.
Furthermore, the same functions of zone 2 also happen in zone 1, so
the function of zone 1 is to maintain and stabilize river bank. The streamside
vegetation or buffer strips have a direct influence on dissolved chemicals.
Recently, a lot of researcher’s articles denoted that the buffer strip can
provide us its function, and play as a protector for the water quality of the river if
its width is between (10 - 60) meters, at least [49]. Also, trapping or removing
various non-point source pollutants from over land and shallow subsurface
flowing in the same time [12]. This area (riparian buffer) provides many benefits
like decreasing soil erosion [3] storage and recycling of organic matter and
nutrients [2]. Moreover, it is providing habitat and nursery functions for fish and
wildlife [3]. Therefore; riparian area has interaction with water and land of the
rich riparian vegetation to receiving waters [17]. Also, in terms of nitrate nitrogen
and organic carbon, [16] showed that the buffer strip can reduce the nitrogen
flow that comes from corn field which is located at the stream side.
Furthermore, [25] showed that the buffer strip can reduce nitrogen,
calcium, nitarate nitrogen and magnesium which come from the agricultural areas
of the river in both sides. Other researchers like [24], indicated some net
percentages of buffer strip prospect to intercept some parameters, such as N 68
%, Ca39 %, P 32 %, Mg 23 %, Cl 7 %, and K 6 %.
[20] Found that the (10) meters of buffer strip width, can reduce
effectively the concentration of phosphoric acid. In addition, many researchers
[24] indicated that the riparian forest zone can remove or absorb the majority of
23
phosphorus and nitrogen flowing from farmland, tea garden and it can intercept
about 70-90 % of total nitrogen and nitrate-N in the width of 20 meters of
riparian zone.
In terms of Pesticides, this kind of contaminants may be held on the
surface of material, like soil particles. This phenomenon is called adsorption. But,
we will concentrate on the Pesticides which are being taken inside a material, by
a plant, this process is called absorption.
On the other hand, there are another function for buffer strips, These
functions include stabilizing stream channels, providing erosion control by
regulating sediment storage, transport, and distribution; providing organic matter
(e.g., leaves and large woody debris) that is critical for aquatic organisms;
serving as nutrient sinks for the surrounding watershed; providing water
temperature control through shading; reducing flood peaks; and serving as key
recharge points for renewing groundwater supplies [30]. Finally, Buffer strips
also provide habitat for a large variety of plant and animal species.
Also, in terms of TSS, according to [5] they conducted their study
using many type of vegetation and they found that all buffer vegetation types
reduced runoff contaminants. The mean ranged from under 40% reduction for the
Plum/Fallow plots, to over 75% reduction for the Plum/Grass plots.
In this study, we are looking for another function for buffer strip, we
will focus only on the zone 1 and to observe its function to remove and intercept
some of pollutants. Moreover, we will study the buffer strip influence on river
water quality. We will concentrate on some parameters which are considered as
important parameters in Johor River are Biochemical Oxygen Demand,
Dissolved Oxygen, Total Suspended Solid and PH.
24
The ability of a buffer zone 1 to provide its functions will depend on
some factors such as width, length, and type, density, and structure of vegetation
present. Table (2.1) below, shows the effectiveness of buffer strip width and its
efficiency to protect water quality.
TABLE 2.1: Some Recommended Widths of Vegetated Buffer Strips, for Various
Functions. Source from [35]
Function
/
Recommended Width
Improve or protect water quality >15m
>25m
Young et al. (1980)
>30m
Lynch et al. (1985)
Dillaha et al. (1989)
>18m
Nichols et al. (1998)
>10m
Corley et al. (1999)
>4m
Doyle et al. (1977)
>19m
Shisler et al. (1987)
100-1000m
>30m
Bird habitat
Authors
Woodard and Rock (1995)
>9m
Reptile/Amphibian habitat
/
Burbrink et al. (1998)
Rudolph & Dickson(1990)
>165m
Semlitsch (1998)
>135m
Buhlmann (1998)
>60m
Darveau et al. (1995)
>100m
Hodges & Krementz (1996)
>100m
Mitchell (1996)
>100m
Triquet et al. (1990)
>150m Spackman & Hughes (1995)
>500m
Kilgo et al. (1998)
>100m
Keller et al. (1993)
>150m
Vander &deGraaf (1996)
>40m
Hagar (1999)
50-1600m Richardson & Miller (1997)
>50m Whitaker&Montevecchi (1999)
Mammal habitat
Maintain plant diversity
>50m
>30m
Dickson (1989)
Spackman & Hughes (1995)
Maintain an unaltered
microclimatic gradient
>45m
Brosofske et al. (1997)
25
2.7
Sediment Transport Capacity in HEC-RAS
HEC-RAS have sediment transport capacity program used to predict
the transport capacity for non-cohesive sediment for all river length, whether the
river consists of one cross section or more. This program is so important for
researcher to understand some of the physical processes in the rivers. Moreover,
it can calculate the transport capacity based on the properties of bed sediment and
the
hydraulic
parameter,
irrespective
of
the
erosion
and
deposition
considerations.
Sediment transport capacity comprises three types of load, is bed load,
suspended load, and wash load. By HEC-RAS, we intend focus on suspended
load and bed load and not consider wash load in the calculations.
According to [41], Bed load describes particles flowing which are
transported along the bed. It moves by rolling and sliding. Usually, bed load
downstream will be smaller and more rounded than bed load upstream. This is
due in part to attrition and abrasion which cause the stones to bump against each
other and against the river channel, thus removing its rough texture and making it
smaller.
On the other hand, Suspended sediment is one of the major pollutants
of streams [42]. Knowing the sediment yield Information of a river, lead to
provide a useful perspective on the rate of erosion and soil losses in the
upstream catchments [32]. Many methods have been developed for the
estimation of suspended sediment loads in rivers, and the most common method
is the relationship between suspended sediment concentrations and the river
discharge; [15]. Wash load consist of fine materials which are finer than those
found the bed and it is supply from watershed not from the hydraulics of the
river.
26
In term of sediment transport calculation, first we should know the
characteristics of flow near the bed of the river in order to determine the
particles movement on it. It is not easy to determine the actual velocity at the
bed. Therefore, to avoid that, we will use one dimensional model.
To determine the point of initial motion, we have to use shear stress
equation and it is given by this expression:
𝜏𝜏𝑏𝑏 = 𝛾𝛾. 𝑅𝑅. 𝑆𝑆
Where:
𝜏𝜏𝑏𝑏 : Bed shear stress
𝛾𝛾
: Unit weight of water
𝑆𝑆
: Energy slope
𝑅𝑅 : Hydraulic radius
Also, the turbulent fluctuation has influence on the particles
movement and we can measure it by the current-related bed load velocity
equation, as shown below:
Where:
𝑢𝑢∗
𝜏𝜏𝑏𝑏
𝑢𝑢∗ = �
𝜌𝜌
𝑜𝑜𝑜𝑜
: Current-related bed shear velocity
𝑢𝑢∗ = �𝑔𝑔𝑔𝑔𝑔𝑔
27
On the other hand, there are many factors which can also affect the
particles movement, such as shape, size, roughness characteristics, and fall
velocity. Generally, the standard sediment transport equation can be represented
as shown below:
𝑔𝑔𝑠𝑠𝑠𝑠 = 𝑓𝑓(𝐷𝐷, 𝑉𝑉, 𝑆𝑆, 𝐵𝐵, 𝑑𝑑, 𝜌𝜌, 𝜌𝜌𝑠𝑠 , 𝑠𝑠𝑠𝑠, 𝑑𝑑𝑖𝑖 , 𝑝𝑝𝑖𝑖 , 𝑇𝑇)
Where:
𝑔𝑔𝑠𝑠𝑠𝑠 : Sediment transport rate
𝐷𝐷
𝑉𝑉
𝑆𝑆
𝐵𝐵
𝑑𝑑
𝜌𝜌
: Depth of flow
: Average channel velocity
: Energy slope
: Effective channel width
: Diameter of particles
: Density of water
𝜌𝜌𝑠𝑠 : Density of sediment particles
𝑠𝑠𝑠𝑠 : Particle shape factor
𝑑𝑑𝑖𝑖
𝑝𝑝𝑖𝑖
𝑇𝑇
: Geometric mean diameter of particles
: Fraction of particles size in the bed
: Temperature of water
28
2.7.1
Fall Velocity
Sediment particle fall velocity is one of the parameters used in all
sediment transport functions. It is mean the average settling velocity of a particle
when it is fallen in quiescent water. There are many factors affecting fall
velocity such as suspended sediment concentration, strength of turbulence, size
and shape of sediment, relative density between fluid and sediment, fluid
viscosity, and sediment surface roughness.
Several methods have been developed to compute the sediment
particle fall velocity. And only three methods available in HEC-RAS are:
•
Toffaleti
•
Rubey
•
Van Rijn
Toffaleti's equation is used by employing Rubey's formulation:
Where:
𝜔𝜔𝑠𝑠 = 𝐹𝐹�𝑑𝑑𝑑𝑑(𝐺𝐺 − 1)
2
36𝑣𝑣 2
36𝑣𝑣 2
𝐹𝐹 = � + 3
−� 3
𝑔𝑔𝑑𝑑 (𝐺𝐺 − 1)
3 𝑔𝑔𝑑𝑑 (𝐺𝐺 − 1)
Where:
𝜔𝜔𝑠𝑠
𝑔𝑔
: Fall velocity of sediments
: Acceleration due to gravity
29
𝐺𝐺
𝜐𝜐
: Specific gravity of sediment=2.65
: Kinetic viscosity of water
Last equation, used to the particles with diameter, d, between (0.06251) mm, and F = 0.79 for particles greater than (1) mm. Figure (2.3) below
recommended by U.S. Interagency Committee, When any of the other sediment
transport formulas are used.
Figure 2.4: The relationship between particle sieve diameter and its fall velocity
30
2.7.2 Sediment Transport Function
There are many used and accepted sediment transport function which are
discovered until now in this field. Such as the common functions are Schoklitsch
Bedload Formula, Kalinske BedloadFormula, Meyer-Peter and Miiller Formula,
Rottner Bedload Formula, Einstein Bedload Formula, Laursen Bed Material Load
Formula, Colby Bed-Material Load Formula, Einstein Bed-Material Load
Formula, Toffaleti Formula and many more. In this study, we will conduct one of
the methods which are available in HEC-RAS, is Toffaleti method. These
methods are:
•
Toffaleti
•
Ackera-White
•
Meyer-Peter Muller
•
Laursen
•
Engelund-Hansen
•
Yang
2.7.2.1
Toffaleti Mehtod
This method is used to determine bed-material discharge. It is
developed by Toffaleti based on the concepts of Einstein with three modifications
are:
1- Velocity distribution in the vertical is obtained from an expression
different from that used by Einstein.
2- Several of Einstein's correction factors are adjusted and combined.
3- The height of the zone of bed load transport is changed from Einstein's
two grain diameters
31
This method breaks the suspended load distribution into vertical
zones, replicating two-dimension sediment movement. Sediment transport is
being defined in four zones. These zones are upper, middle, lower, and bed
zones. Each zone has independent sediment transport and the total sediment is the
summation of all the four zones. Toffaleti defines his bed-material discharge as
total river sand discharge, even though he defines the range of bed-size material
from 0.062 to 16 mm.
The general transport equations are represented as below:
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠
𝑅𝑅 1+𝑛𝑛 𝑣𝑣 −0.756𝑧𝑧
− (2𝑑𝑑𝑚𝑚 )1+𝑛𝑛 𝑣𝑣 −0.756𝑧𝑧
�11.24�
= 𝑀𝑀
1 + 𝑛𝑛𝑣𝑣 − 0.756𝑧𝑧
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠
𝑅𝑅 1+𝑛𝑛 𝑣𝑣 −𝑧𝑧
𝑅𝑅 0.244𝑧𝑧 𝑅𝑅 1+𝑛𝑛 𝑣𝑣 −𝑧𝑧
− �11.24�
�11.24�
��2.5�
�
= 𝑀𝑀
1 + 𝑛𝑛𝑣𝑣 − 𝑧𝑧
𝑅𝑅 1+𝑛𝑛 𝑣𝑣 −𝑧𝑧
𝑅𝑅 0.244𝑧𝑧 𝑅𝑅 0.5𝑧𝑧 1+𝑛𝑛 𝑣𝑣 −𝑧𝑧
� �
−� �
�11.24�
�𝑅𝑅
�
2.5
2.5
= 𝑀𝑀
1 + 𝑛𝑛𝑣𝑣 − 𝑧𝑧
𝑔𝑔𝑠𝑠𝑠𝑠 = 𝑀𝑀 (2𝑑𝑑𝑚𝑚 )1+𝑛𝑛 𝑣𝑣 −0.756𝑧𝑧
𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 𝑧𝑧𝑧𝑧𝑧𝑧𝑧𝑧
𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 𝑧𝑧𝑧𝑧𝑧𝑧𝑧𝑧
𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈 𝑧𝑧𝑧𝑧𝑧𝑧𝑧𝑧
𝐵𝐵𝐵𝐵𝐵𝐵 𝑧𝑧𝑧𝑧𝑧𝑧𝑧𝑧
𝑀𝑀 = 43.2𝐶𝐶𝐿𝐿 (1 + 𝑛𝑛𝑣𝑣 )𝑉𝑉𝑉𝑉 0.756𝑧𝑧−𝑛𝑛 𝑣𝑣
𝑔𝑔𝑠𝑠 = 𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠 + 𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠 + 𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠 + 𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠
Where:
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠
: Suspended sediment transport in the lower zone in unit ton/day/ft
32
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠 : Suspended sediment transport in the middle zone in unit ton/day/ft
𝑔𝑔𝑠𝑠𝑠𝑠𝑠𝑠 : Suspended sediment transport in the upper zone in unit ton/day/ft
𝑔𝑔𝑠𝑠𝑠𝑠
: Bed load sediment transport in unit ton/day/ft
𝑀𝑀
: Sediment concentration parameter
𝑅𝑅
: Hydraulic radius
𝑑𝑑𝑚𝑚
: Median particle diameter
𝑔𝑔𝑠𝑠
𝐶𝐶𝐿𝐿
: Total sediment transport in unit ton/day/ft
: Sediment concentration in the lower zone
𝑛𝑛𝑣𝑣
: Temperature exponent
𝑧𝑧
: Exponent describing the relationship between the sediment and hydraulic
characteristic
33
2.8
Water Quality Modeling
Water quality modeling involves the prediction of water pollution
using mathematical simulation techniques. A typical water quality model consists
of a collection of formulation representing physical mechanisms that determine
position and momentum of pollutants in a water body. The main objective of
water quality modeling is to describe and predict the observed effect of change in
a river system. It is used to the changes in the water quality parameters due to
point and non-point sources [26].
There are many water quality modeling’s being used to predict easily
water quality of a river such as BASINS, STREAM, EPD-RIV1 [27], CEQUALW2 [6], WASP5, HSPF, and QUAL2E. In this study, we will use QUAL2E to
predict Johor river water quality. The QUAL2E model is a comprehensive stream
water quality model and this version developed from QUAL-Ι and QUAL- ΙΙ. It
was developed by United State Environment Protection Agency (USEPA) for
waste load allocation and other pollution evaluation. It is applicable with wellmixed dendritic streams where the major transport mechanisms of both advection
and dispersion are only significant along the longitudinal axis of flow for a
stream. Moreover, this model can simulate more than (15) water quality
parameters which are Dissolved oxygen (DO), Biological oxygen demand, algae,
temperature, organic nitrogen, ammonia, organic phosphorus, nitrate, nitrite,
coliform, an arbitrary non conservative constituent and three conservative
constituents.
The model solves the time-variable water quality parameter under
steady, non-uniform flow. It can be applied to steady state and diurnal timevariation situations. It has been applied in the United State and other countries
such as Chile, Italy, Spain, Slovenia, India, and South Africa. It is a simple model
with comprehensive dissolved oxygen dynamics, nutrient, and
algae.
34
Furthermore, it is easy to understand as well as easy to use and yields a complete
documentation.
The program simulates changes in flow conditions along the stream
by computing a series of steady-states water surface profiles. The calculated
stream-flow rate, velocity, water depth, and cross-sectional area serve as basis for
determining the heat and mass fluxes into and out of reach computational
element due to flow.
Mass balance determines the concentration of conservative minerals,
coliform bacteria, and non-conservative constituents at each computational
element. Material fluxes, major processes included in mass balance are
transformation of nutrient, algal production, benthic and carbonaceous demand,
atmospheric reaeration, and the effect of these processes on the dissolved oxygen
balance. Moreover, the primary internal sink of dissolved oxygen in the model is
biochemical oxygen demand (BOD). The major sources of dissolved oxygen are
algal photosynthesis and atmospheric reaeration.
Furthermore, by operation the model dynamically, the user can study
the effects of daily variations in data on water quality primarily dissolved oxygen
and temperature as well as can study daily dissolved oxygen variations due to
algal growth and respiration. However, the effects of dynamic forcing functions
like point load and headwater, cannot be modeled in QUAL2E.
The model divided the stream into a network of reaches, headwater
and junctions. The most functional subdivision in the reach, which are the
stretched of stream that have uniform hydraulic characteristics. Then, each reach
will be divided into computational elements of equal length. Reaction rate
coefficient, initial condition and incremental flow data are constant for all
computational elements within a reach. To run the QUAL2E program, few input
35
related with the characteristics of the river should be known to analyze the data
easily. Below, is the data which required for this model:
a. Hydraulic data
b. Initial conditions
c. Computational elements flag field data
d. Reach identification and river mile/kilometer data
e. Biochemical oxygen demand and dissolved oxygen rate constants
f. Incremental inflow
g. Headwater sources
h. Point source or withdrawal
JOHOR River has high velocities and lead to make each crosssectional segment is well mixed and QUAL2E will use a one-dimensional
transport model Equation as shown below:
1 𝜕𝜕
𝜕𝜕𝜕𝜕
1 (𝐴𝐴𝑥𝑥 𝑉𝑉)
𝑆𝑆𝑐𝑐
𝜕𝜕𝜕𝜕
=
�𝐴𝐴𝑥𝑥 𝐷𝐷𝑙𝑙 � −
+
+ 𝑅𝑅
𝜕𝜕𝜕𝜕 𝐴𝐴𝑥𝑥 𝜕𝜕𝜕𝜕
𝜕𝜕𝜕𝜕
𝐴𝐴𝑥𝑥 𝜕𝜕𝜕𝜕
𝐴𝐴𝑥𝑥 ∆𝑥𝑥
Where:
C
: is the concentration of a water quality constituent.
Ax : is the cross section area.
V : is the current velocity.
Sc : is the external load.
DL : is the longitudinal dispersion coefficient.
R
: represents all the water quality kinetics, is deemed appropriate.
36
Figure 2.5: QUAL2E computational network
2.9
Limitation of QUAL2E
QUAL2E has been designed to be relatively general program.
However, certain dimensional limitations were imposed during program
development [18]. These limitations are as in Table 2.2 below:
37
Table 2.2: limitation of data in QUAL2E
2.10
Limitation data
Value
Reaches
A maximum of 50
Computational elements
Total 500 / Maximum 20 per reach
Headwater elements
A maximum of 10
Junction elements
A maximum of 9
Point source and withdrawal elements
A maximum of 50
QUAL2E Calibration and Validation
A typical water quality modeling process consists of data collection,
model formulation, calibration and validation [22]. The data and model
formulation phases affect the results of the subsequent calibration phase.
However, for a successful modeling practice, the calibration phase should give
the optimum model parameters possible. During calibration or validation steps
some problems in the data set or model formulation may be revealed. According
to the information gathered about the system during these steps, additional
sampling or model reformulation may be considered [22].
It is essential to consider the possible reaction of the water body
before taking any action on it. As surface waters are complex environmental
system, it is hard to understand and predict their behavior. The attempts to predict
the response of water bodies to pollution loads originating from human activities
resulted in the development of mathematical model. These models quantitatively
describe the physical, chemical and biological behavior of water bodies through a
collection of mathematical relationships that contain many parameters such as
reaction rate coefficient, biological and chemical constants that are specific to the
38
system modeled. So, in order to apply them, they must be able to define the
system in the most accurate way.
The model was further applied to determine strategies that would help
in bringing down the water quality of the river to an acceptable limit. The
simulations were made to explore how the water quality would change with
change in loads as well as environmental modifications such as flow
augmentation to the river. The scenario helped to visualize the effectiveness of
approaches intended to prevent pollution before their actual implementation.
2.11
Applications of QUAL2E
[26] has performed QUAL2E model on Selangor River and the
calibration and validation was done and the result indicate that the simulated
water quality parameters tend to be over predicted and accurate in the urban sub
watershed in Rawang River and other sub watershed , respectively. The result of
the study indicated the importance of water quality models in an integrated
watershed management approach. The use of QUAL2E for Selangor River
emphasized the need of such models to achieve a target river water quality for
future generation.
While [1], states that QUAL2E model has been applied to predict the
pollution in Sebulung River. She only concentrated on two parameters, BOD and
DO. This model will help in predicting the future condition of the river and take
rehabilitation measures before it become worst.
Moreover, [37] also mentioned that QUAL2E model will help in
deciding the development of water resource management of the Tebrau River and